The present invention relates to a roving package wrapper having a roving package formed by winding roving such as glass fiber.
Roving is used as a reinforced material for fiber reinforced plastic (hereinafter referred to as FRP). The roving is wound to form a hollow cylinder i.e., a package of roving. The hollow cylindrical package of roving is typically provided to the user.
Conventionally, a glass fiber roving package is made as follows. Glass strands are separately pulled from a plurality of cakes of glass fiber strands installed on a creel. Some tension is applied to each of strands and they are gathered into a bundle. The bundle passes through a guide and a tension gate and then through a traverse guide eye of the winder. The bundle is wound on a mandrel of the winder while transversely moving the guide eye. With winding the bundle onto the mandrel, some tension is applied thereto so as to wind the bundle tight. This prevents the roving package from collapsing and the roving from forming loops, when the roving being pulled from the inside of the package reaches the outermost layer of the package. If the collapsing of the roving package or the formation of the loops occurs, the undesired wastes occurs and the continuous production process cannot be attained.
The winder is equipped with the rotating mandrel and the guide eye reciprocated close to the surface of the package being formed on the mandrel. The mandrel is linked with a drive adjustment mechanism which control the rotation speed of the mandrel, so as to maintain the circumferential speed at a constant value even if the winding is advanced. Further, in order to wind the roving tightly, the package being formed on the mandrel is continuously pressed by a depressing roller. The package thus made is typically sized into a diameter of 240-280 mm, a height of 250-300 mm and a weight of 13-20 Kg.
In another conventional method for manufacturing roving package, known as a direct winding roving, a great number of glass fibers spun from a bushing are bundled up and wound directly. This method is used for manufacturing roving which requires a uniform tension applied to strands and which is indispensable for space development or producing FRP parts having high performance. By using a bushing provided with 1,000 hole or more, it is possible to produce a fiber of 10 microns diameter. The winder is an important of that used for producing normal glass fiber, and incorporates a special controller at the end of the traverse portion so that the roving package can be square at its end, or a square-end package can be formed. The rotation speed of the collet is programmed to thereby achieve a predetermined winding speed. With this manufacturing process, the dimensions and weight of manufactured package are the same as those given above.
The roving packages produced in this manner are wrapped in heat shrinkage film in order to avoid damage during transportation or handling. On transportation, plural packages stacked up vertically are lined up in parallel so as to form a rectangular parallelepiped as a whole. These are then covered in corrugated cardboard to avoid damage and the outer surfaces of these are bound tightly with heat shrinkage film.
When roving is used for manufacturing FRP by such methods as SMC, filament winding or spray up, roving 2 is pulled out from the inside of the roving package 1 as shown in FIG. 7, and then fed into cutter (not shown). Further, in order to continuously use packages, the winding end 2a of roving of the outermost layer of one package is pulled out of the central upper opening of the heat shrinkage film which wraps the package, and then the winding end 2a is, in advance, tied to the winding top 2b of roving of another roving package 1 to be subsequently pulled out.
However, the roving package as manufactured above suffers from problems in that, in the case where the roving is pulled from the inner side of the package and the thickness of roving, which remains therein, becomes smaller as the roving gets closer to the end of the roving package, with a light external force to pull out the roving, the roving which remains as outermost layer of the package collapses under its own weight, and loops and/or complicated knots are formed. As a result, these loops or knots are grasped in the guide of the supply equipment, thereby rendering it impossible to pull out the roving continuously.
This trouble results in undesired stoppage of production, and further, in the case where SMC sheets or the like is manufactured by simultaneously employing a plurality of roving, the amount of supplied roving is caused to be decreased, so that the products result in unevenness of glass contained therein.
In particular, since large-sized packages have their greater outer diameters and heights, the roving, which remains therein, collapses frequently during the pulling out process. A solution of the above problems has been therefore expected to be found urgently.